A straw to be attached to a beverage container preferably should be longer than the depth of the container to prevent the straw from falling into the container during drinking. However, a straw sufficiently long to be convenient for drinking all of the contents of a particular container will necessarily be longer than the beverage container itself, and consequently, it is difficult to attach such a straw to the container in a convenient manner. As a result, there is a demand for a straw which is contractible for attachment to the container and extensible for use. The extensible and contractible double straw well known in the art consists of an inner straw and an outer straw of a relatively simple construction. The outer straw has one end formed with a portion of reduced diameter while the inner straw has one end portion formed with an enlarged diameter so that these two portions engage each other when these inner and outer straws have been fully telescopically extended. In consequence, practical use of such extensible and contractible double straws of prior art has often been accompanied by problems described in the following paragraphs.
For drinking, such a double straw is telescopically extended to form a unitary straw and then inserted into the beverage container. Proper extension of the double straw is achieved by extending the inner straw in a normal direction or in the direction toward the front end. However, the inner straw becomes separated from the outer straw if the inner straw is carelessly extended in the opposite direction. Additionally, the double straw of the prior art has not been provided with means to hold the straw in fully extended position or to prevent the straw from readily contracting. Thus, a pressure unintentionally applied to the straw during drinking might cause the complete straw to drop into the container.
In view of such problems, the inventor has already proposed in Japanese Utility Model Application No. 58-127196 an extensible and contractible double straw consisting of an inner straw having its base end formed as a portion of enlarged diameter and an outer straw having its front end formed as a portion of reduced diameter so as to assure engagement of the base end of the inner straw with the front end of the outer straw when these inner and outer straws have been telescopically fully extended, wherein the outer straw is provided adjacent the front end thereof with an inwardly directed stopper to prevent the inner straw from retracting into the outer straw and the outer straw is further provided at the base end with a portion of reduced diameter to prevent the inner straw from slipping out of or separating from the outer straw.
The improved straw disclosed in the above-mentioned application is adequately effective in that the inner straw is effectively prevented from separating from the outer straw and, in the extended state, the inner straw is held against retracting back into the outer straw. However, even this improved straw has proved to have several problems due to said inwardly directed stopper which has been construted merely as an inwardly directed projection. More specifically, the portion of enlarged diameter formed along the base end of the inner straw cannot move smoothly beyond said stopper when said inner straw is withdrawn from the outer straw for fully extending the double straw, also, sometimes the double straw may be used without complete engagement of the inner straw with the outer straw. There has occurred even a case in which the inner straw was withdrawn with excessive force to overcome the difficulty in moving the base end of the inner straw beyond said stopper and, as a consequence, said base end of enlarged diameter is moved beyond the front end of the outer straw which was formed as the portion of reduced diameter.
The present invention provides a further improvement in view of the above-mentioned problems, in that the inner straw is effectively prevented from readily separating from the outer straw and the double straw is reliably restrained against easily contracting again once the double straw has been fully extended with the base end of the inner straw forming the portion of enlarged diameter smoothly sliding beyond the inwardly directed stopper of the outer straw.
According to the present invention, this object is achieved, in an extensible and contractible double straw consisting of an inner straw having its base end formed as a portion or enlarged diameter and an outer straw having its front end formed as a portion of reduced diameter so as to assure engagement of the base end of the inner straw with the front end of the outer straw when these inner and outer straws have been fully extended in a telescopic manner. In this arrangement, the outer straw is provided, adjacent the front end thereof, with an inwardly directed stop to prevent the inner straw from retracting into the outer straw and the outer straw is further provided at the base end with a portion of reduced diameter to prevent the inner straw from separating from the outer straw. In this improvement, the inwardly directed stop provided by the outer straw includes a gentle slope facing the base end and a steep slope facing the front end of said outer straw.